29 August 2011

Who should I be: a slender old man or a youngish fat man?

Between aging and obesity,
or how protection from oxygen radicals contributes to overweightKirill Stasevich, Compulenta

Oxygen radicals, which, due to their oxidative activity, often harm the cell and bring the aging of the body closer, help us maintain a figure: an increase in the content of radicals in special neurons as they become saturated causes cells to signal the end of lunch.

In the modern world, the problem of overweight is becoming an epidemic, with which it is still unclear what to do. The causes of obesity are called a great many, but the first place is invariably held by ordinary overeating. However, scientists immediately face another question: what makes a person eat more than necessary?

Researchers from Yale University (USA) came to a paradoxical and even somewhat ambiguous conclusion: according to them, free radicals, which are represented by active oxygen forms in living cells, make us overeat. These compounds, which are a by-product of biochemical reactions to produce energy, pose quite a significant danger to the body. Free oxygen radicals are very aggressive, have a high oxidizing ability and can damage biomolecules; their attack on DNA can lead to mutations and disorder of the processes underlying the functioning of the cell. It is believed that free radicals are responsible for the aging of the body: accumulating damage in the cell leads to the fact that cells fail, and with age their vacancies remain unfilled.

In cells, there are special systems designed to intercept oxygen radicals, in particular, peroxisomes – special membrane bubbles filled with enzymes that neutralize dangerous molecules.

Peroxisomes (green) and fat cells (red);
peroxisome enzymes are involved not only in the neutralization of free radicals,
but also in the oxidation of fats (photo TheJCB).

As researchers write in the journal Nature Medicine (Diano et al., Peroxisome proliferation–associated control of reactive oxygen species sets melanocortin tone and feeding in diet-induced obesity), an increase in the number of peroxisomes in hypothalamus cells makes you eat more. Special secretory neurons are responsible for the feeling of satiety; in experimental mice, these cells were activated after eating. The signal for them is the hormone leptin, which is synthesized by fat cells, and glucose; having caught these molecules, neurons understand that enough nutrients have entered the body. But if there was an increased number of peroxisomes – free radical traps in such neurons, then in this case the animals continued to eat beyond need.

Studies have shown that such mice retain a high content of the appetite hormone neuropeptide Y, the release of which usually decreases in response to an increase in blood glucose and leptin. Peroxisomes suppressed the activity of appetite-controlling neurons, which led to overeating; normally, the content of free oxygen radicals increased in such cells as they were saturated, and the neurons gave the order for the "end of lunch".

Researchers have yet to find out the details of the mechanism, but the alternative, needless to say, is disappointing. Since free radicals work for aging, then our choice is to be young and fat or aging quickly, but with a beautiful figure.

This, according to the authors, is the reason that until now it has not been possible to find an effective way to prevent obesity without serious side effects, since this inevitably led to an increase in the content of aggressive oxidants in cells. But scientists will still try to find out whether it is still possible to make our neurons feel saturated without attracting free oxygen radicals to it.

Prepared based on materials from Yale University: Free Radicals Crucial To Suppressing AppetitePortal "Eternal youth" http://vechnayamolodost.ru


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